Room Dimensions & Splayed Ceiling Question

[AlexT]

Wanted to make sure about this CR design dimensions
Length: 12 ft
Width: 10 ft
Height: 10 ft (but will be vaulted downwards after 5 ft)
See drawing.

Would this design cause acoustical problems since starting point for the height and the width are both 10 ft?

[knightfly]

Yes, you'd have a LOT of double and triple-stacked modes with that. Better would be if you could get AVERAGE dimensions of (say) 13,11,9 feet - that would give ZERO coincident modes, and pretty smooth distribution of the modes overall. I'm not sure you could EVER treat that "near cube" enough to get a balanced sound field, and still have room enough for you and your gear inside.

Also, with regard to your CR window design -

http://www.audio-muziek.nl/audiotechniek/acoustics.pdf

HTH... Steve

[AlexT]

Yes, you'd have a LOT of double and triple-stacked modes with that.

Thanx Steve,
So this would be a problem even with the ANGLED ceiling?

[knightfly]

Yeah, just not as MUCH of a problem. Modes don't go away with angled walls/ceilings, they just shift; about the best GUESS we can do without building and testing, is to use the AVERAGE dimension for rough calculations.

Another thing is that even multiples of feet in dimensions (like 8'x10'x12) will cause modes to stack up (all 3 of those dim's will share modes at some multiple) whereas, odd combinations of feet (like 9'x11'x13') do NOT do that, at least until the harmonics are so high in frequency that it doesn't matter any more.

Did you see the comments about splayed glass in the link? Steve

[AlexT]

Did you see the comments about splayed glass in the link? Steve

Yes I did Steve.
I was planning on splaying them open towards the bottom (opposite of the top drawing I posted).
I will be using sconce lighting directed towards the ceiling, so reflection shouldn't be much of a problem.
Should I just set them straight not splayed?

Regarding my room dimensions:
Actual dimensions after all the sheetrock and hardwood floors will be:
Length: 11.6 ft
Width: 9.6 ft
Height: 9.6 ft splayed down to 8.6 ft

Are these dimensions still risky?

[knightfly]

Lighting, glass - if possible, set up your lighting as close as possible to what it will end up - stretch some clear plastic across your window frames, one piece in each room the window serves, just tape or staple it in place; if you can still see thru both pieces of plastic without noticeable glare, I wouldn't tilt EITHER piece of glass.

If, however, you will NOT be soffit mounting your main speakers, you may want to tilt the glass up toward the ceiling to lessen any early reflections that may be caused by diffracted sound from either speaker bouncing off the CR window and returning to the mix position; if you ARE planning on soffiting the mains, there shouldn't even BE a diffraction problem, only the OTHER early reflections from side walls, ceiling, console...

Those finished dimensions are better, but will likely still have a noticeable modal imbalance at around 80-100 hZ - 2 of the three tangential modes that may cause the problems are related to ceiling height, and since that's splayed (and I used the average height) they should be less noticeable than if that surface were parallel to the floor.

Considering the (possible) problem frequency and type of modes, there's a really good chance that using floor-to-ceiling corner absorbers will smooth things out acceptably - but the only way you'll know is to build it and measure/listen; by then, it would be too late to change things.

If you lower the front of the ceiling by another foot to a finished height of 7-1/2 feet, the whole thing smooths out and will likely allow you to get the room sounding good with less treatment... Steve

[AlexT]

Thanks Steve,
I will NOT be soffit mounting my speakers, so I guess I will have to angle my windows.

Considering the (possible) problem frequency and type of modes, there's a really good chance that using floor-to-ceiling corner absorbers will smooth things out acceptably.

Should these corner absorbers be with slot resonators or plane?
Should they be built in every corner (front & back)?
How about side slot resonators? Are they needed for this size room?

[knightfly]

For that size room, I'd stick to the plan at the bottom of this page -

http://www.johnlsayers.com/HR/index1.htm

HTH... Steve

[AlexT]

For that size room, I'd stick to the plan at the bottom of this page - http://www.johnlsayers.com/HR/index1.htm HTH... Steve

Thanks Steve,
That is the plan I’m going with.
Should I build Slot Resonators for the side walls or is it better to just hang Panel Absorbers?
Space Limitations

[knightfly]

Tried to respond to this yesterday, but the site went away;

If you're space limited, you can do OK with something like 2" rockwool at first reflection points (including ceiling), I'd space it off the wall by another 2" for better low mid absorption... Steve